MOLYBDENUM(VI) DIOXODIHALIDES - AGREEMENT WITH EXPERIMENT AND PREDICTION OF UNKNOWN PROPERTIES THROUGH DENSITY-FUNCTIONAL THEORY

Density functional calculations are reported for the molecular structu res, harmonic vibrational frequencies, UV/visible spectra, and ore-tra nsferability of MoO(2)X(2) (X = F, Cl, Br, I). Available experimental data have been used to check the validity of the theoretical calculati ons. Given the good agreement between theory and gas-phase experiment, predictions have been issued for the less studied members of this fam ily of compounds. Furthermore, electronic spectra of the full series h ave been computed for the first time. For all transitions studied, exc itation energies decrease in the order F > Cl > Br > I. Finally, the l abilization of Mo-O bonds generated by the HOMO-LUMO transition, which is related to the oxygen-atom transfer reaction in the active site of molybdenum oxidoreductases, was also investigated. For MoO2Cl2 and Mo O2Br2 compounds, the HOMO-LUMO transition yields a considerable length ening of the Mo-O bond, yet not requiring a large excitation energy. ( C) 1997 John Wiley & Sons, Inc.